technical solutions to the problem of contaminated cabin air · solutions to contaminated cabin air...

AIRCRAFT DESIGN AND SYSTEMS GROUP (AERO)

Technical Solutions

to the Problem of Contaminated Cabin Air

Deutscher Luft- und Raumfahrtkongress 2018

German Aerospace Congress 2018

Friedrichshafen, Germany, 04.-06.09.2018s://doi.org/10.5281/zenodo.1186593

Dieter Scholz Hamburg University of Applied Sciences


Friedrichshafen, 04.-06.09.2018

Dieter Scholz:

Solutions to Contaminated Cabin Air 05.09.2018, Slide 2

Aircraft Design and Systems Group (AERO)

Abstract

Purpose – This presentation gives an introduction to the problem of contaminated cabin air and points out possible

solutions especially by looking at carbon filters placed in the main path of the bleed air from the engine to the cabin

("total cabin air filtration") in additon to filters in the cabin air recirculation path. Maintenance issures related to the topic

are also considered.

Design/methodology/approach – The literature review is complemented with own explanations, thoughts and

derivations.

Findings – There is a real health and flight safety risk due to contaminated cabin air. For the infrequent flyer the risk is

very low. Also aviation statistics are not dominated by cabin air related accidents. Nevertheless, a bleed air based air

conditioning system can be regarded as applying a fundamentally wrong systems engineering approach. A substantial

improvement of the situation can only be reached with filters added to the large fleet of existing airplanes. A full solution,

however, requires airconditioning with outside air and dedicated compressors.

Research limitations/implications – The study is based primarily on references.

Practical implications – Passengers and crew are made aware of the risk of cabin air contamination based on

technical facts. Given detailes of technical solutions contribute to the scientific discussion.

Social implications – Better knowledge of the problem should enable passengers and crew to maintain a firm position

in the sometimes heated discussion.

Originality/value – Engineering based information with a critical view on the topic seems to be missing in public. This

presentation contributes filling this gap.

© This work is protected by copyright

The work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0

International License: CC BY-NC-SA

http://creativecommons.org/licenses/by-nc-sa/4.0

Any further request may be directed to Prof. Dr.-Ing. Dieter Scholz, MSME

E-Mail see: http://www.ProfScholz.de



Dieter Scholz:



Contents

Technical Solutions to the Problem of Contaminated Cabin Air

• Introduction

• Cabin Comfort and Cabin Air Quality – Health and Flight Safety Implications

• Jet Engine Oil

• Air Conditioning Technology

• Jet Engine

• Maintenance – The Case of Engine/APU Oil Contamination

• Engineering Design Principles from SAE

• Solution: Sensors and Filters

• Solution: ECS Principles

• Summary

• Contact

• References



Dieter Scholz:



Introduction



Dieter Scholz:



Introduction

(Flight International 2014)

...



Dieter Scholz:



Introduction

... but ...

A controversial issue! (Telegraph 2017)



Dieter Scholz:



Definition: Aircraft Cabin Air

Aircraft cabin air is the air in the cabin of an aircraft. The air in the cockpit is included in

this definition. In pressurized cabins it is the air inside the pressure seals. Pressure control

is such that cabin pressure is reduced down to a pressure equivalent to 8000 ft (referring

to the ICAO Standard Atmosphere) as the aircraft climbs. In unpressurized aircraft cabins

the air is at ambient pressure. Temperature control is done by heating or cooling as

required. Venting ensures frequent exchange of cabin air with fresh air from outside. In

addition, cabin air can be recirculated and filtered. When flying at high altitudes, cabin air

is at similar low relative humidity as the air outside.

Definition: Quality

Degree to which a set of inherent characteristics fulfills requirements.

(ISO 9001)

Introduction



Dieter Scholz:



Definition: Contamination

The process of making a material unclean or unsuited for its intended purpose, usually by

the addition or attachment of undesirable foreign substances.

Adapted from (Wiktionary 2018)

The presence of a minor and unwanted constituent (contaminant). Related to health: A

harmful intrusion of toxins or pathogens e.g. in food, water, or air.

Adapted from (Wikipedia 2018a)

Definition: Fume Event (Rauchereignis)

In a fume event, the cabin and/or cockpit of an aircraft is filled with fume. The fume

originates from the bleed air and enters the cabin via the air conditioning system. Air

contamination is due to fluids such as engine oil, hydraulic fluid or anti-icing fluid. A Fume

Event includes a Smell Event. Note: Other reasons for fume in the cabin are possible.

The term "fume event", however, is generally used as defined here.

Adapted from (Wikipedia 2018b)

Introduction



Dieter Scholz:



Introduction

Fume Event on US Airways Flight 432 Phoenix to Maui in 2010

Video on: https://youtu.be/AZqeA32Em2s

Note:

Smell events (without fumes) are much more frequent than fume events.

Health effects have been reported from smell events alone (where patients never encountered a fume event) .



Dieter Scholz:



Definition: Smell Event (Geruchsereignis)

A fume event without visible fume or smoke, but with a distinct smell usually described as

"dirty socks" from the butyric acid originating from a decomposition of the esters that are

the base stock of the synthetic jet engine oil. Note: Other reasons for smell in the cabin

are possible. The term "smell event", however, is generally used as defined here.

Definition (ECA): Smoke & Fume / Smell Event (cabin air contamination)

An incident may cause only fume, only smell or both. The European Cockpit Association

(ECA) explains: "In the context of the ICAO circular [ICAO Circular 344 'Guidelines on

Education Training and Reporting Practices related to Fume Events'], fumes and odours

are deemed to be synonymous, and the term 'fume(s)' includes both fumes and odours." (ECA 2017)

Definition (IATA): Cabin Air Quality Event (CAQE)

"Cabin air quality events (CAQEs) [are] particularly ... the so-called fume events" (smoke,

fumes / odours).

(IATA 2017)

Introduction



Dieter Scholz:



Proposed new Definition:

Definition: Cabin Air Contamination Event (CACE)

In a Cabin Air Contamination Event (CACE) the air in the cabin and/or cockpit of an

aircraft is contaminated. Sensation of the contamination can be from vison (fume/smoke),

olfaction (smell/odor), a combination of typical symptoms experienced by several

passengers and/or or crew or by related measurements of CO, CO2, ozon or other

"harmful or hazardous concentrations of gases or vapours" (CS-25.831).

Typical symptoms following a CACE (ECA 2017)

Intention with the new definition: Detach the definition from merely human sensation. Allow also drastic health

degradation to define the event. Objective measurements would certainly be best, but are usually not available.

Introduction



Dieter Scholz:



Introduction

Definition: Condensation Event

In a condensation event, warm and humid air in the cabin

mixes with cold air from the air conditioning system. This

usually happens during departure, when the cabin is still

filled with air from outside and starts to mix with cold air

leaving via the cabin outlets. Note: Do not confuse this

with a fume event!

Condensation on A319 ("EGGD", http://i56.tinypic.com/2gwhoif.jpg) Condensation on AirAsia flight AK6303 with A320 from

Langkawi (LGK) to Kuala Lumpur (KUL). Departure in tropical

rainforest climate ("PlaneHunter", http://bit.ly/2oUJYKP)

(GENFAM A320)



Dieter Scholz:



Civil Aviation Authority (CAA), UK, 2017:

"CABIN AIR CONTAMINATION INFORMATION SHEET FOR PATIENTS"

Where does the cabin air supply come from?

... from the engines ...

What are the causes of contamination of the cabin air supply?

The cabin air may be contaminated when an oil seal fails, allowing jet oil or hydraulic fluid

to leak into the bleed air supply. This can result in an oil mist or odour in the aircraft which

is sometimes described as smelling like ‘sweaty socks’ ...

What are the concerns regarding contamination of the cabin air ...?

... both short and long term adverse effects on health ...

Which chemicals might contaminate bleed air?

It is difficult to determine exactly what substances are present in contaminated bleed air.

When jet oils and hydraulic fluid are subjected to very high temperatures, they break

down to produce other compounds including potentially harmful substances such as

carbon monoxide, aldehydes (that can irritate the airways) and various acidic compounds

(that produce unpleasant odours). Aircraft engine oils also contain small amounts of

organophosphates, ... toxic effects, particularly on the nervous system ...

Introduction



Dieter Scholz:



Civil Aviation Authority (CAA), UK, 2017:

"CABIN AIR CONTAMINATION INFORMATION SHEET FOR PATIENTS"

What are the short term health effects?

... irritation of the eyes, nose and throat, headache, dizziness and tingling in the hands,

feet and face ...

What are the long term health effects?

Symptoms that have been reported include:

• neurological symptoms such as headaches, fatigue, weakness, problems with balance,

pain, numbness, memory problems

• psychological symptoms such as depression, anxiety, poor concentration

• skin problems, respiratory or gastro-intestinal symptoms are also occasionally reported

... remains an area of scientific uncertainty.

(CAA 2017)

Introduction



Dieter Scholz:



How Do We Know about Oil in the Cabin?

Oil has left traces on its way from the engine to the cabin interior:

1. Oil traces in bleed duct

2. Oil traces in air conditioning ducts

3. Oil traces in recirculation filters

4. Oil traces on cabin surfaces (wall panels, seats, ...)

Evidence collected in: Scholz 2017

Introduction

1. 2. 3. 4.



Dieter Scholz:



Cabin Comfort and Cabin Air Quality –

Health and Flight Safety Implications



Dieter Scholz:



Cabin Comfort and Cabin Air Quality – Health and Flight Safety Implications

(A350 XWB News 2012)

VOC: Volatile Organic Compounds are (organic chemicals – i.e. including carbon) contained in many

products and can be released from these products into the surrounding air. Regulations limit VOCs.

SVOC: Semi-Volatile Organic Compound (Eurofins 2017)

Cabin Air Quality Cabin Comfort



Dieter Scholz:



Potential Concerns Related to Cabin Air Quality

• Cabin Pressure Can effect people with cardio-respiratory diseases from lack of oxygen

• Relative Humidity Temporary drying of skin, eyes, and mucous membranes

• Carbon Monoxide High concentrations during air-quality incidents. Frequency is believed to be low.

CS 25.831: Concentration must be lower than 50 ppm.

• Carbon Dioxide Concentrations are generally below FAA regulatory limits. Associated with increased

perceptions of poor air quality. CS 25.831: Concentration must be lower than 0.5%.

• Ozone Elevated concentrations on aircraft without ozone converters. Airway irritation and

reduced lung function. CS 25.832: Concentration < 0.25 ppm resp. 0.1 ppm.

• Pesticides From aircraft “disinsection" with pesticides.

• Engine Oil Fumes from hot engine oil may enter the cabin via the bleed air system.

• Hydraulic Fluids Frequency of incidents is expected to be relatively low. Mild to severe health effects.

• Deicing Fluid Hazardous substance. Skin sensitizing and irritant.

• Airborne Allergens Exposure frequency is not known. Irritated eye and nose; sinusitis;

acute increases of asthma; possible anaphylaxis.

• Nuisance Odors Can be present on any flight.

Adapted from (NRC 2002)




Dieter Scholz:



Possible Sources Affecting Cabin Air Quality

(Airbus 2017)




Dieter Scholz:



Health Effects: Occupational Health & Flight Safety

may be experienced soon after exposure or, possibly, years later:

• Long-term heath effects:

• to passengers

• to crew => occupational health (OH) => CS 25.831

usually related to

Time-Weighted Average (TWA)

Permissible Exposure Limits (PEL)

• Immediate health effects:

• to passengers

• to cabin crew

• to cockpit crew => flight safety implications can lead to:

injury or death of

• passenger

• crew => CS 25.1309

(Eurofins 2017, EASA CS-25)




Dieter Scholz:



Occupational Health – Long Term Health Effects

EASA CS-25: CS 25.831 Ventilation

(a) Each passenger and crew compartment must be ventilated ... to enable crewmembers to perform their duties

without undue discomfort or fatigue.

(b) Crew and passenger compartment air must be free from harmful or hazardous concentrations of gases or

vapours. In meeting this requirement, the following apply: (1) Carbon monoxide concentrations in excess of one part

in 20000 parts of air [50 ppm] are considered hazardous. For test purposes, any acceptable carbon monoxide

detection method may be used. (2) Carbon dioxide concentration ...

"EASA is of the opinion ... only applicable for ... CO and CO2"

Remark: EASA's interpretation of certification rules: The cabin is allowed to be contaminated with other substances!

"The BFU is of the opinion that 'harmful concentration' should be interpreted ... to mean that health impairments

(including long-term) through contaminated cabin air should be eliminated."

"The BFU is of the opinion that a product [aircraft] which has received a type certificate by EASA should be designed in a

way that neither crew nor passengers are harmed or become chronically ill."

Bundesstelle für Flugunfalluntersuchung

German Federal Bureau of

Aircraft Accident Investigation

(BFU 2014)




Dieter Scholz:



Flight Safety Implications – Immediate Health Effects

There have been several (much debated) critical flight instances,

but so far (luckily) no death (due to flight safety implicatons) and no hull loss.

Compare e.g. with the issue "Degraded Manual Flying Skills" (Flight International 2017)

From 2000 to 2017:

• 19 fatal accidents

• 2012 fatalaties

Remark:

There are certainly several issues in

aviation of more pressing nature than

"cabin air quality / contamination",

however, the suffering of individuals

(potentially / probably) due to cabin air

contamination can not be ignored (may it

just be for ethical reasons), because the

underlying deficits in aircraft system

design are a fact (see below) and need to

be solved.




Dieter Scholz:



Jet Engine Oil



Dieter Scholz:



Jet Engine Oil

(Cannon 2016)

This warning was changed in 2004 (Michaelis 2012) to:

"This product is not expected to produce adverse health effects under normal conditions of use ... Product may

decompose at elevated temperatures ... and give off irritating and/or harmful ... gases/vapours/fumes. Symptoms from

acute exposure to these decomposition products in confined spaces [aircraft cabin] may include headache, nausea, eye,

nose, and throat irritation."

(Exxon 2016c)

TCP

Material Safety Data Sheet (MSDS)

FIRST AID MEASURES, INHALATION

Remove from further exposure [in a fume

event?]... Use adequate respiratory protection

[not available for passengers!]. If respiratory

irritation, dizziness, nausea, or unconsciousness

occurs, seek immediate medical assistance. If

breathing has stopped, assist ventilation with a

mechanical device or use mouth-to-mouth

resuscitation.

(Exxon 2016c)

Judging Jet Engine Oil Based on

Warnings Given by Manufacturer



Dieter Scholz:



T = tri (3)

D = di (2)

M = mono (1)

TOCP

DOCP

MOCP

H3C

, they are the toxic isomers.

OC

MC

PC

(Winder 2001)

Tricresyl Phosphate (TCP)

Jet Engine Oil

TOCP: H3C



Dieter Scholz:



Jet Engine Oil

Actual OCP Content of the TCP --- Isomerization

Ramsden 2013a:

OC content in the TCP:

TCP Class 1: 30% (about 1930)

TCP Class 2: ?

TCP Class 3: 3% (about 1958, "modern TCP")

TCP Class 4: 0.3 % (since 1992, "conventional TCP")

TCP Class 5: 0,03 % (since 1997, "low-toxicity TCP")

------------------------

TCP Class 6: 0 % (since 2017, "zero-OCP TCP") Remark / Introduction: Proposal for a new class definition

Ramsden 2013 / Imbert 1997:

Another possibility is that isomerization of the TCP takes place within the engine during operation.

Megson 2016:

... temperatures of 400 °C. These temperatures have the potential to alter the composition of the original oil and

create other toxic compounds.

There is currently a large degree of uncertainty as to what compounds are produced and how toxic they are

through inhalation in the vapour phase at high altitudes.



Dieter Scholz:



No tri-ortho cresyl phosphate TOCP isomers were detected.

No di-ortho cresyl phosphate DOCP isomers were detected.

No mono-ortho cresyl phosphate MOCP isomers were detected.

TCP Class 6: No OCP Content (2016)

Jet Engine Oil

Actual OCP Content Measured

A comparison of fresh and used aircraft oil for the identification of toxic substances ...

Summation of TPC (%): 4.85 4.68 4.20 2.45 2.91 2.92

(Megson 2016)



Dieter Scholz:



"a ... list of 127 compounds [VOC] was ... identified ... ". The hazard profile is given in Appendix 6:

How much Oil Gets into the Cabin?

EASA Study 2017: AVOIL (EASA 2017b)

AVOIL – Characterisation of the toxicity of aviation turbine engine oils after pyrolysis



Dieter Scholz:



Air Conditioning Technology



Dieter Scholz:




Air Conditioning Basics

Increasing Temperature of Air due to Compression from Ambient to Cabin Pressure

1) compress the air => increasing temperature of air

2) cool the air

-100

-50

0

50

100

150

0 10000 20000 30000 40000 50000

tem

pera

ture

, t;

p

ressu

re,

p

flight altitude, H [ft]

t_ISA [°C]

p_ISA [kPa]

p_cab [kPA]

t_comp,cab [°C]

tropopause, H_t

cabin altitude, H_cab



Dieter Scholz:




(dm/dt)in

(dm/dt)out

low

pressure

"normal"

pressure

1) compress the air

2) cool the air

=> Temperature

Control

3) release the air

=> Pressure Control:

out > in: pressure goes down

in > out: pressure goes up

Air Conditioning Basics

Temperature Control, Pressure Control, Ventilation




Dieter Scholz:




Air Conditioning with Recirculation




Dieter Scholz:




Temperature

Control (ii)

A320

bleed air

50 %

outflow valve

50 % recirculation

recirculation

fan

A320

Temperature

Control,

Pressure

Control,

Ventilation

2) Air Cooling

Temperature

Control

Adapted from (FCOM A320)

hot

cold

warm

bleed air from engine compressor



Dieter Scholz:



Jet Engine



Dieter Scholz:



Engine Overview

Jet Engine

Engine Alliance GP7000

(Assuntos Militares 2013)

bearing (example)



Dieter Scholz:



Engine Air and Oil System

Jet Engine

based on (Exxon 2016b) (oil)

(air & oil)

(oil & air) & oil

& oil

(oil & air)

Normal operation of

engine seals:

1. The "drain"

discharges oil.

2. The "dry cavity"

contains oil.

3. Air and oil leak from

bearings into the

bleed air.

=> Engines leak small

amounts of oil by

design!

1.

2.

3.

3.



Dieter Scholz:



Engines Longer on Wing

Labyrinth-Seal Clearances Increase as Engines Age

"Labyrinth-seal clearances naturally increase as an engine ages. As this occurs – due to

rubbing under vibration, gyroscopic torque, rough landings or any g-load factor, the

engine air flow increases, resulting in even higher oil consumption" (Exxon 2016a) and

hence leakage into the bleed air.

Jet Engine

The figure shows increasing time to first

shop visit of CFM56-7B engines. It follows:

During a period of 10 years (2004 to 2014)

maintenance practice changed such that

engines stay on the wing almost twice as

long without shop visit and seal

replacement.

(AviationWeek 2016)



Dieter Scholz:



Maintenance

The Case of Engine/APU Oil Contamination



Dieter Scholz:



Trouble Shooting and Cleaning

Aircraft Trouble Shooting

US Airways Flight 432 Phoenix to Maui (2010)

(https://youtu.be/AZqeA32Em2s)

Maintenance

Aircraft Duct Cleaning

(Airbus 2017)

(Airbus 2013)



Dieter Scholz:



Maintenance

Special situation at an engine start of a new aircraft coming from

Final Assembly Line at Airbus, Germany (Balk 2018)



Dieter Scholz:





Maintenance

Pack Cleaning

(Airbus 2013)

Cleaning



Dieter Scholz:





Maintenance

Aircraft released back into service over night

after an (oil based) fume/smell event

are most probably not cleaned as instructed by Airbus,

because ducts can not be removed

from behind the panels in this short time.

Aircraft Duct Cleaning

Cleaning

(Airbus 2013)



Dieter Scholz:



Engineering Design Principles

from SAE



Dieter Scholz:



SAE ARP 1796: Engine Bleed Air Systems for Aircraft

(first edition 1987, A in 2007, B in 2012)

Bleed Air Quality: Requirements should be imposed on the engine manufacturer

regarding the quality of the bleed air supplied to occupied compartments.

Under normal operating conditions:

The engine bleed air shall be free of engine-generated objectionable odors, irritants,

and/or toxic of incapacitating foreign materials.

Following any type of engine … failure, the engine bleed air shall not contain the above

substances to a harmful degree.

… or bleed air systems should incorporate a bleed air cleaner.

Engineering Design Principles for Air Conditioning from SAE



Dieter Scholz:



Engineering Design Principles for Air Conditioning from SAE

SAE AIR 1168-7: Aerospace Pressurization System Design

(first edition: 1991, A in 2011)

“Compressor bleed from turbine engines is attractive because of the mechanical

simplicity of the system.” However, “oil contamination ... can occur in using

compressor bleed air from the main engines.” “Popular opinion regarding the

risk of obtaining contaminated air from the engine may preclude its use for

transport aircraft, regardless of other reasons.”

SAE AIR 1116: Fluid Properties

(first edition: 1992, A in 1999, B in 2013)

“Until adequate toxicity data are available precautions must be observed in handling any unfamiliar

fluid.”

This means:

It is not the task of passengers and crew to prove that engine oils and hydraulic fluids as used today are

dangerous. Just on the contrary, industry has to prove that fluids and equipment are safe before

they intend to use them, because standards have been agreed among engineers already long time

ago, not to use bleed air on transport aircraft!



Dieter Scholz:



Solution:

Sensors and Filters



Dieter Scholz:



Get Informed => Personal CO Detector. Get Protected in the Cabin => Breathing Mask

• The Carbon Monoxide (CO) level in normal operation is much lower

than the limit of 50 ppm (specified in CS 25.831). Failure cases did not

occur during these measurements.

• We know much CO is present in the cabin during a Fume Event.

The elevated CO concentration indicates the severity of the event.

Therefore, crew should carry their personal CO detector, be

informed and make decisions accordingly!

• If smoke is present, checklists tell pilots to put on their oxygen mask. In

such a case, cabin crew should consider wearing a personal

breathing mask protecting against nerve gas.

EASA 2017b, p.74

Normal CO Situation Failure Case: Fume Event


Cabin crew protection !

Get CO Detector and Breathing Mask

Solution: Sensors and Filters



Dieter Scholz:



KKmoon CO Meter: Test on Ground and Measurements on Aircraft

Test in car exhaust gas => up to 77 ppm CO (Video: https://youtu.be/iwqcgPdht-w)



Measurements on aircraft:

Generally: 0 ppm

One measurement: 5 ppm

(measured at cabin outlet on A320, during take-off, HAM, RWY 33)

Cabin limit:

50 ppm




Dieter Scholz:



Filters to Remove TCP and VOC

Pall has several treetment solutions for cabin air on offer:

• Carbon Filter

• Photo Catalytic Oxidization (with UV light)

• Catalytic Converters (oxidization). Location is possible:

• upstream of the pack,

• downstream of pack,

• at recirculation filter

(reduced efficiency compared to a filter in line with the pack – see next page)

Pall offers Odour/VOC Removal Filters

• The carbon adsorbent is effective at adsorbing volatile organic compounds (VOC).

Test results have shown a removal efficiency of 65% ... 73% when challenged with

TCPs in the gaseous phase. Carbon adsorbents have some effectiveness with ozone

but not with carbon monoxide (CO). Removal of these compounds from the cabin air is

by adsorption on to carbon based filters. (Pall 2011)

Application of carbon filters:

• 33 HEPA-Carbon filters have been added (so far) to A321 aircraft at Lufthansa Group.

(Lufthansa 2017)

• EasyJet started in 2016 to retrofit their fleet of A320 family aircraft with Pall Aerospace

PUREair Advanced Cabin Air Filters (A-CAF) combining HEPA filters and carbon filters

to remove Volatile Organic Compounds (VOC) from aircraft cabin air. (Pall 2016)

• Pall carbon filters are installed on the B757 cargo fleet of DHL.

Carbon filters are installed in place of the air ducts leading to

the cockpit. EASA issued an STC for the installation. (EASA 2010)

Schematic of carbon Filter

(Pall 2011)




Dieter Scholz:



filtration rate, xfil

Example calculation:

• The Pall carbon adsorbent is effective at adsorbing volatile organic compounds with a removal efficiency of 65% ...

73% when challenged with TCPs in the gaseous phase. (Pall 2011)

• The A320 has a recirculation rate of 50%.

• With a filtration rate, xfil = 0,7 and a recirculation rate, xre = 0,5 the filter reduces the incoming concentration to 58,9%.

But: How Efficient are Filters in the Recirculation Path?

refil

re

incont

cabcont

xx

x

x

x

11

1

,

,

re

incont

cabcont

fil

xx

x

x

1

:1for

,

,




Dieter Scholz:



outm

inm

totm

outrere mm ,

inm

inrem ,

filter

Derivation:

Efficiency of Filters in the

Recirculation Path





Dieter Scholz:



outm

inm

totm

outrere mm ,

inm

inrem ,

filter

refil

re

incont

cabcont

xx

x

x

x

11

1

,

,

re

incont

cabcont

fil

xx

x

x

1

:1for

,

,

reincontrefilcabcont xxxxx 111 ,,

Derivation:

Efficiency of Filters in the

Recirculation Path





Dieter Scholz:



outm

inm

totm

outrere mm ,

inm

inrem ,

filter

Filter in the Recirculation Path


Example :

• The Pall carbon adsorbent is effective at adsorbing volatile organic compounds with a removal efficiency of 65% ...

73% when challenged with TCPs in the gaseous phase. (Pall 2011)

• The A320 has a recirculation rate of 50%.

• With a filtration rate, xfil = 0.7 and a recirculation rate, xre = 0.5

the filter reduces the incoming concentration down to 58,9%.




Dieter Scholz:



EasyJet to filter toxic air in cabins

Andrew Gilligan

September 17 2017, 12:01am,

The Sunday Times

https://www.thetimes.co.uk/article/easyjet-to-filter-toxic-air-in-cabins-6qzrf6sjx

The budget carrier is the first to take action over links to an illness long denied

by airlines.

EasyJet said ‘health concerns’ led it to design a new air filtration system for testing on

aircraft next year.

"Total Air Filtration"

Video

https://youtu.be/1-uzihfve_4

and full article

http://bit.ly/2x1uUzv

also on

http://CabinAir.ProfScholz.de



Dieter Scholz:



50 %

outflow valve

50 % recirculation

recirculation

fan

cross bleed

valve (normally closed)

Engine 1 APU Engine 2

Full

Filtration

(Option: 1)

VOC Filter

Combined

HEPA & VOC Filter (HEPA-Carbon Filter)

Filtration aft of

source (engine /

APU). Filtration

in recirculation.

18.06.03.0

)1(,

,

recircfil

incont

cabcontfx

x

x

=> reduces incoming pollutant

concentrations to 18%




Dieter Scholz:



50 %

outflow valve

50 % recirculation

recirculation

fan

cross bleed



Full

Filtration

Option: 2

VOC Filter

Combined


Filtration before or

directly aft of Pack

Flow Control Valve.

Filtration in recircu-

lation.

18.06.03.0

)1(,

,

recircfil

incont

cabcontfx

x

x






Dieter Scholz:



50 %

outflow valve

50 % recirculation

recirculation

fan

cross bleed



Full

Filtration

Option: 3a

VOC Filter

Combined


Filtration of cold

air and of hot trim

air. Filtration in

recirculation.

refil

re

recircxx

xf

11

1

18.06.03.0

)1(,

,

recircfil

incont

cabcontfx

x

x






Dieter Scholz:



50 %

outflow valve

50 % recirculation

recirculation

fan

cross bleed



Full *

Filtration

Option: 3b

VOC Filter

Combined


*

Filtration of cold

air only. Hot trim

air is not filtered.

Filtration in re-

circulation.




Dieter Scholz:



Full *

Filtration

Option: 3b

*

Filtration of cold air only.

Hot trim air is not filtered.

Filtration in recirculation.

On the occasion of the same selected temperature in all three zones, trim air is mostly used

in the cockpit. It is used also in the forward zone (FWD), if the cabin layout has a business

class. Air from the packs is controlled to such a (low) temperature to just meet the cooling

needs of the "hottest" zone, which is usually the aft zone (AFT) because it has most

passengers per cabin area.

We assume:

FWD and AFT zone have no trim air.

Demanded and achieved cabin temperature in all zones is 21 °C.

Cooling needs are met with a temperature in the mixing unit of 10 °C.

Bleed air (aft of the precooler) is at 200 °C.

Mass flow into the cockpit is much smaller than into the cabin.

Trim air mass flow is much smaller than mass flow from the mixing unit into the cabin.

This leads to:

Flow rate into the cockpit consists of 5.8% trim air and 94.2% air from the mixing unit.

Relative concentration of pollutants:

18.06.03.0

)1(,

,

recircfil

incont

cabcontfx

x

x



Cabin FWD and AFT zone:

Cockpit zone:


concentrations to only 23% 23.0)058.01(18.0058.0

1,

,

,

,

•

m

m

x

x

m

m

x

x

tot

trim

incont

cabcont

tot

trim

incont

cockpitcont




Dieter Scholz:



50 %

outflow valve

50 % recirculation

recirculation

fan

cross bleed



Full

Filtration

Option: 4

VOC Filter

Combined


Filtration of air

directly before it

is entering the

respective cabin

zone. Filtration in

recirculation.

18.06.03.0

)1(,

,

recircfil

incont

cabcontfx

x

x






Dieter Scholz:



Solution:

ECS Principles



Dieter Scholz:



Solution: ECS Principles

Cabin Pressurization Principles and Solutions – Overview

Overview • First Jet Aircraft used a "blower" or "turbocompressor" (TC). The TC is the coupling of a turbine with a compressor. Bleed air from the

engine compressor drives the TC turbine. The TCs compressor compresses outside air to meet the pressurization requirements of the cabin.

The hot compressed air needs to be cooled. This can be done with a "vapor cycle system" (as known from the refrigerator).

• Current Aircraft make use of bleed air directly. It is compressed so much that it contains enough energy to also drive the pack that cool

the bleed air down to temperatures considerably less than 0°C.

• The Boeing 787 uses electrical power to drive an electric motor to drive a compressor. The energy is extracted from the engine by

means of shaft power driving a generator. No bleed air is used. The engine is "Bleed Free".

(Michaelis 2010)

Solution?

Problem?

Solution!



Dieter Scholz:



Solution B787!

Electrical (Bleed Free) Cabin Air Supply

(Boeing 2007)

The "Pack" of the B787's Environmental Control System (ECS) is powered by electric motors (M) to

compress ambient air up to cabin pressure and to push the air through the heat exchangers (HX) for

cooling. The power for the electric motors is produced by generators (SG) connected to the aircraft's

engine and APU. After compression and cooling the air is delivered to the cabin.




Dieter Scholz:



More Electric A320?




Dieter Scholz:



More Electric A320 with Electrical (Bleed Free) Cabin Air Supply?

The Electrical Environmental Control System (E-ECS) was developed by Liebherr-Aerospace Toulouse SAS, Toulouse

(France), Liebherr’s center for air management systems. The E-ECS is equipped with a new type of motorized turbo

compressor (50 kW) which enables to use directly external air (bleed less) for air conditioning. The power electronics

ensure the speed control of the motorized turbo compressor and offer synergy capabilities with other electrical loads to

optimize the overall electrical power consumption on board the aircraft. The interaction between air intake and the turbo-

compressors and the performance of the system in all operating conditions was tested in a flight test campaign with

Airbus A320-Prototyp MSN001 from June 3 to June 24, 2016. E-ECS will also contribute to fuel burn reduction.

(Liebherr 2016)

Copyright Liebherr




Dieter Scholz:



Summary

• There is sufficient evidence for a problem of contaminated cabin air:

engines leak oil by design,

oil can be traced on its way from the engine into the cabin, ...

CAA, Airbus, ... document the problem,

Lufthansa, EasyJet, ... take action

• Short term partial technical solution: Carbon filter:

a) in the duct to the cabin and

b) attached to the recirculation filter

suitable for retrofit

• Long term full technical solution: Bleed-free architecture with direct air intake

and dedicated compressor

suitable only for newly designed aircraft




Dieter Scholz:



Contact

[email protected]

http://www.ProfScholz.de





Dieter Scholz:



References

A320 FCOM

Airbus: A320 – Flight Crew Operating Manual (FCOM)

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Airbus 2013

Airbus: In-Service Information, Environmental Control System Decontamination, A319/A320/A321, 2013

Airbus 2017

Airbus: In-Service Information, Cabin Air Quality Troubleshooting Advice, All Aircraft, 2017

Assuntos Militares 2013

Assuntos Militares: Engine Alliance GP7000 (picture), 2013. – URL: https://goo.gl/images/gYIW31;

http://www.assuntosmilitares.jor.br/2013/01/pratt-fornecera-turbinas-embraer.html

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wing-advan




Dieter Scholz:



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Dieter Scholz:



References

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Condor Flugdienst GmbH, British Airways

EASA 2017b

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Pyrolysis, 2017. –

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Dieter Scholz:



References

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library/resources/jet-engine-oil-consumption

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Dieter Scholz:



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Dieter Scholz:



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Dieter Scholz:



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All online resources have been accessed on 2018-09-10 or later.

Quote this document:

Scholz, Dieter: Technical Solutions to the Problem of Contaminated Cabin Air. German Aerospace Congress,

Friedrichshafen, Germany, 04.-06.09.2018. – Presentation No. 0270, download from: http://CabinAir.ProfScholz.de

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